Retinitis pigmentosa (RP) is a group of disorders that affects about 1 in 4,000 people. In most cases patients have night blindness, and mid-peripheral followed by far peripheral vision loss, then a contracting central visual field (VF; extent of vision), tunnel vision and eventual blindness. There are no treatments and current management aims to slow progression and to provide rehabilitation. Potential interventions to restore vision include artificial retinal implants and other visual prostheses, gene therapy, and stem cells. While these interventions tend to focus on restoration of central vision, consideration should be given to providing peripheral vision. For those not at end-stage disease, enhancement of peripheral vision could provide benefit by assisting with functional ability and perhaps by slowing disease progress. Further, the requirements of peripheral vision are more consistent with the quality of vision that is available from current and near-future interventions. A main purpose of peripheral vision is locomotion, providing information about the environment for safe mobility. Patients with RP often have peripheral islands of vision, which are regions in the far periphery on either side and often below. Clinical experience suggests that these peripheral islands are valuable for mobility. However, there have been no published studies that examine the value of peripheral islands. Before providing peripheral vision through some form of vision restoration, the value of peripheral islands should be evaluated. We will use a very large set of existing data from over 600 patients with RP who participated in one of five to seven studies. Their responses to one or more of three vision function questionnaires will be merged using Rasch analysis into a single linear scale that will measure functional ability. Their measured visual fields will be analyzed using a novel archetypal analysis approach. This approach decomposes visual fields into fundamental elements and patterns from which peripheral islands can be quantified. The primary aim of the study will be to determine the impact of the presence of peripheral islands on functional ability. We will employ two approaches to this analysis, firstly using mixed-effects regression and, secondly, using an established Bayesian variable selection approach. This project is a collaboration between Russell Woods and Tobias Elze at the Schepens Eye Research Institute, Michael Sandberg at Massachusetts Eye and Ear Infirmary, and Konrad Pesudovs at Flinders University.